python - Python unittest - setUpClass() 给我带来了麻烦 - 为什么我不能这样继承？

Question

我有如下的单元测试代码：

import unittest

class MyUnitTest(unittest.TestCase):
    def setUpClass(self):
        do_something_expensive_for_all_sets_of_tests()

class MyFirstSetOfTests(MyUnitTest):
    def setUpClass(self):
        super(MyFirstSetOfTests, self).setUpClass()
        do_something_expensive_for_just_these_first_tests()

    def test_one(self):
        ...

    def test_two(self):
        ...

class MySecondSetOfTests(MyUnitTest):
    def setUpClass(self):
        super(MySecondSetOfTests, self).setUpClass()
        do_something_expensive_for_just_these_second_tests()

    def test_one(self):
        ...

    def test_two(self):
        ...

if __name__ == '__main__':
    unittest.main()

当我尝试运行此代码时，我收到如下错误：

======================================================================
ERROR: setUpClass (__main__.MyFirstSetOfTests)
----------------------------------------------------------------------
TypeError: unbound method setUpClass() must be called with MyFirstSetOfTests instance as first argument (got nothing instead)

----------------------------------------------------------------------

Answer 1

setUpClass 必须是类方法。从文档中：

在单个类运行测试之前调用的类方法。setUpClass以类作为唯一参数调用，并且必须装饰为classmethod()：

@classmethod
def setUpClass(cls):
    ...

有关更多详细信息，请参见类和模块装置。

您的版本缺少@classmethod装饰器：

class MyUnitTest(unittest.TestCase):
    @classmethod
    def setUpClass(cls):
        do_something_expensive_for_all_sets_of_tests()

class MyFirstSetOfTests(MyUnitTest):
    @classmethod
    def setUpClass(cls):
        super(MyFirstSetOfTests, cls).setUpClass()
        do_something_expensive_for_just_these_first_tests()

抛出错误是因为在classMyFirstSetOfTests.setUpClass()上调用，而不是在实例上调用，但是您没有将方法标记为 a ，因此它没有在自动参数中传递。在上面我使用的更新代码中，以反映名称引用了类对象。classmethodselfcls